Laboratory of the chemistry of nitrocompounds(№ 42)

• Chemistry of nitro compounds;
• Chemistry of polynitrogen-oxygen heterocyclic and acyclic systems;
• Synthesis of new high-energy molecular and salt structures;
• Nitration reactions and new nitrating reagents.

✓ A method for the synthesis of a new energetic compound, [1,2,3,4]tetrazino[5,6-e]-[1,2,3,4]tetrazine-1,3,6,8-tetroxide (TTTO), was developed. It was synthesized in ten steps from 2,2-bis(tert-butyl-NNO-azoxy)acetonitrile. The synthetic strategy is based on the sequential closure of two 1,2,3,4-tetrazine-1,3-dioxide rings by generating oxodiazonium ions and their intramolecular reaction with tert-butyl-NNO-azoxy groups. The structure of TTTO was confirmed by single-crystal X-ray diffraction analysis. TTTO is one of the most energetic compounds obtained to date. It is thermally stable (temperature of the onset of intense decomposition is 155 °C , DSC)), has a good density (1.84 g∙cm^–3, gas pycnometer) and a high calculated enthalpy of formation (1028 kcal∙kg^–1). (DOI: 10.1002/anie.201606541)

✓ A simple and effective two-step approach to previously unknown 1,4-dihydro-[1,2,3]triazolo[4,5-d][1,2,3]triazole is developed. This compound is an individual energetic material (d = 1.84 g·cm^–3, ΔH_f° = +1005 kcal·kg^–1, T_onset = 193 °C (all experimental values), D = 8.5 km∙s⁻¹, P = 34 GPa (calculated ones)), but also may serve as a scaffold for the synthesis of structurally diversified related compounds. The precursors of 1,4-dihydro-[1,2,3]triazolo[4,5-d][1,2,3]triazole are previously unknown 5-amino-4-diazo-4H-1,2,3-triazolium chloride and 5-amino-4-diazo-4H-1,2,3-triazole, which can also serve as starting materials for the synthesis of a variety of novel heterocycles. For example, the 5-amino-4-diazo-4H-1,2,3-triazole was used for the regioselective synthesis of a 2,5-disubstituted [1,2,3]triazolo[4,5-d][1,2,3]triazole bearing N₄-tripoid fragment. Overall, the developed approach to 1,4-dihydro-[1,2,3]triazolo[4,5-d][1,2,3]triazole, 5-amino-4-diazo-4H-1,2,3-triazolium chloride and 5-amino-4-diazo-4H-1,2,3-triazole is expected to make these high nitrogen systems more accessible and affordable for design of nitrogen containing fused heterocycles. (DOI: 10.1039/D4NJ04427D)

✓ It was shown for the first time that the interaction of nitroso compounds with salts of O-substituted N-nitrohydroxylamines leads to the formation of corresponding azoxy-oxy [N(O)=N–O] compounds, as exemplified by the reaction of 3-amino-4-nitrosofurazan with the ammonium salt of O-methyl-N-nitrohydroxylamine to give 3-amino-4-(methoxy-NNO-azoxy)furazan. This novel approach turned out to be the most suitable for the multigram synthesis of this aminofurazan. The latter is a precursor for novel energetic (methoxy-NNO-azoxy)furazans, containing nitro, azo, azoxy and methylenedinitramine groups. The resulting substituted (methoxy-NNO-azoxy)furazans have good thermal stability (onset decomposition temperatures 148–238 °C), high experimental enthalpies of formation (1435–2750 kJ∙kg^–1) and acceptable densities (1.57–1.75 g∙cm^–3). We have shown the extent to which introduction of the methoxy-NNO-azoxy group into a molecule can be used to tune the crucial properties of energetic materials (enthalpy of formation and thermal stability). (DOI: 10.1016/j.enmf.2024.08.007)

✓ Two novel methods for the synthesis of energetic substituted furazans, bearing a rare 1,3-dinitro-1,3-diazabutyl group, were elaborated. The starting compounds are easily available aminofurazans and 1-chloro-2-nitro-2-azapropane. The resulting (1,3-dinitro-1,3-diazabutyl)furazans have good thermal stability (onset decomposition temperatures 124–160 °C), high experimental enthalpies of formation (947–1528 kJ⋅kg⁻¹) and acceptable densities (1.60–1.70 g⋅cm⁻³). In terms of detonation performance, all synthesized compounds (detonation velocities D = 8.0–8.3 km⋅s⁻¹, detonation pressures P_C–J = 27–30 GPa) are comparable with pentaerythritol tetranitrate (PETN) (D = 8.3 km⋅s⁻¹, P_C–J = 31 GPa). For novel compounds "structure-property" relationships have been revealed that will allow predicting the key energetic characteristics of hypothetical compounds containing 1,3-dinitro-1,3-diazabutyl explosophoric group. (DOI: 10.1016/j.fpc.2025.09.003)

✓ The simple and concise method for the synthesis of novel energetic furazans containing little-studied explosophoric 5-azido-1,3-dinitro-1,3-diazapentyl moiety
[–N(NO₂)CH₂N(NO₂)CH₂CH₂N₃] has been developed on the basis of easily available aminofurazan derivatives. The novel furazans have good thermal stability (onset decomposition temperatures 115–157 °C), high enthalpies of formation (1459–1914 kJ⋅kg⁻¹) and acceptable densities (1.64–1.73 g⋅cm⁻³). In terms of detonation performance, all synthesized compounds (detonation velocities D = 8.1–8.3 km⋅s⁻¹, detonation pressures P_C–J = 28–31 GPa) are comparable with pentaerythritol tetranitrate (PETN) (D = 8.3 km⋅s⁻¹, P_C–J = 31 GPa). For novel compounds "structure-property" relationships have been revealed that will allow predicting the key energetic characteristics of hypothetical compounds containing 5-azido-1,3-dinitro-1,3-diazapentyl explosophoric group. (DOI: 10.1016/j.fpc.2025.11.008)

✓ A comparative study of experimentally established structures, stability and energetic performance of ammonium and hydrazinium salts of 4H-[1,2,3]triazolo[4,5-c][1,2,5]oxadiazole (triazolofurazan) as well as its N-oxide and N-nitroimide was performed. The aim of this study was to reveal the “structure–property” relationships for triazolofurazan derivatives. It has been demonstrated that triazolofurazan is a perspective and stable platform for the development of new energetic compounds. The contribution of N-oxide and N-nitroimide substituents to changes in the enthalpy of formation, density, heat resistance, and special characteristics is estimated using the example of the obtained salts. (DOI: 10.1039/d4ce00329b)

✓ A method for the synthesis of novel (1-N-alkylnitramino)methoxy-substituted oxetane monomers from the corresponding N-chloromethyl-N-alkylnitramines has been developed. Based on these monomers, new high-energy oligomers were synthesized for a preliminary assessment of their potential. The oligomers were thoroughly characterized using a combination of physicochemical methods, and their common structural features were identified. The novel monomers can be used to produce effective high-energy binders via cationic ring-opening polymerization. (DOI: 10.1016/j.fpc.2024.12.002)

✓ The versatility of the HNO₃–H₂SO₄–Ac₂O system in the annulation reaction of amino-1,2,5-oxadiazoles is demonstrated. In addition to previously obtained unsubstituted cinnoline oxides and their nitro derivatives, a series of R-[1,2,5]oxadiazolo[3,4-c]cinnoline-5-mono- and 1,5-dioxides with various substituents (R = Br, F, CH₃, CF₃) in various positions of the arene ring were obtained from corresponding 3-amino-4-(R-aryl)-furazans and 4-amino-3-(R-aryl)-furoxans.

The crystal structures of five new compounds were determined. The crystal packings were compared with each other and with those of previously studied molecules, revealing common motifs regardless of the type or position of the R substituent. Specifically, the fluoro derivative forms layers isostructural with those in unsubstituted mono- and dioxides, differing only in their arrangement within the P21 and P21/c space groups. The methyl derivatives of both furazan and furoxan exhibit a planar-layer structure, meaning that the presence of an exocyclic oxygen atom has virtually no effect on the layered packing in the crystal. The unsubstituted portion of the heterocyclic core tends to form repeating isostructural motifs, such as dimers, chains, and layers. (DOI: 10.1039/d4ce01068j)

✓ Methods for the synthesis of new heterocyclic systems consisting of 1,2,3,4-tetrazine 1,3-dioxide annulated with 1,3a,4,6a-tetraazapentalenes have been developed. The synthesis started from (tert-butyl-NNO-azoxy)acetonitrile and involved the closure of the 1,2,3,4-tetrazine 1,3-dioxide ring first and then formation of the 1,3a,4,6a-tetraazapentalene system. Derivatives of the new polycyclic systems, nitrated at the benzene ring, were also obtained. A number of the synthesized tetraazapentalenes exhibit high thermal and chemical stability and may be of interest as energetic compounds. (DOI: 10.1002/ajoc.201800545)

✓ A method for the synthesis of a new energetic compound, 7-nitro-3-(nitro-NNO-azoxy)-[1,2,4]triazolo[5,1-c][1,2,4]triazin-4-amine, containing amino and nitro-NNO-azoxy groups in adjacent positions, has been developed based on (tert-butyl-NNO-azoxy)acetonitrile. This is the first nitro-NNO-azoxy compound exhibiting thermal stability acceptable for practical application (the onset temperature of intense decomposition is 154 °C, DSC). It has a high calculated enthalpy of formation (580 kcal kg^–1), high density (1.875 g cm^–3), and sensitivity to mechanical stress at the level of that for pentaerythritol tetranitrate. (DOI: 10.1002/ejoc.201900314)